Video footage shown by Chinese news outlets showed bystanders watching helplessly as intense flames flared out of the three-story building containing the karaoke bar and climbed up its walls.

The Qingyuan police said they detained a suspect, a 32-year-old man named Liu Chunlu, at 10:50 a.m. Tuesday.

A reporter for CCTV, the state-run broadcaster, said online that the fire had been started by a person who had been in a quarrel beforehand. That report, which did not cite the source of the account, said the person had used a motorbike to block the only entrance to the karaoke club, then lit the fire at the door.

The China News Service, a state-run news agency, said that the police in Qingyuan — an industrial and commercial center — had blocked off roads to catch the person responsible.

The police did not say how many of the dead were found inside the bar. Often karaoke bars in China feature small rooms padded with carpet, and at least some of the dead may have been trapped in such rooms.

The deadly fire is likely to prompt another round of calls from the Chinese government to tighten up safety, especially in the crowded fringes of cities and industrial zones where fires often break out.